https://github.com/datastax/java-driver/java-driver-core: A driver for Apache Cassandra(R) 2.1+ that works exclusively with the Cassandra Query Language version 3 (CQL3) and Cassandra's native protocol versions 3 and above.
  • Various (DataStax) 
/*
 * Copyright DataStax, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.datastax.oss.driver.api.core.metrics;

import com.codahale.metrics.Metric;
import com.codahale.metrics.MetricRegistry;
import com.datastax.oss.driver.api.core.metadata.Node;
import edu.umd.cs.findbugs.annotations.NonNull;
import edu.umd.cs.findbugs.annotations.Nullable;
import java.util.Optional;


A wrapper around a MetricRegistry to expose the driver's metrics. 
This type exists mainly to avoid a hard dependency to Dropwizard Metrics (that is, the JAR can
be completely removed from the classpath if metrics are disabled). It also provides convenience
methods to access individual metrics programatically.

/**
 * A wrapper around a {@link MetricRegistry} to expose the driver's metrics.
 *
 * <p>This type exists mainly to avoid a hard dependency to Dropwizard Metrics (that is, the JAR can
 * be completely removed from the classpath if metrics are disabled). It also provides convenience
 * methods to access individual metrics programatically.
 */
public interface Metrics {

  
Returns the underlying Dropwizard registry.

Typically, this can be used to configure a reporter.

See Also:
@leaks-private-api
/**
   * Returns the underlying Dropwizard registry.
   *
   * <p>Typically, this can be used to configure a reporter.
   *
   * @see <a href="http://metrics.dropwizard.io/4.0.0/manual/core.html#reporters">Reporters
   *     (Dropwizard Metrics manual)</a>
   * @leaks-private-api
   */
  @NonNull
  MetricRegistry getRegistry();

  
Retrieves a session-level metric from the registry.

To determine the type of each metric, refer to the comments in the default 
reference.conf (included in the driver's codebase and JAR file). Note that the method does not check that this type is correct (there is no way to do this at runtime because some metrics are generic); if you use the wrong type, you will get a ClassCastException in your code: 

// Correct:
Gauge<Integer> connectedNodes = getNodeMetric(node, DefaultSessionMetric.CONNECTED_NODES);
// Wrong, will throw CCE:
Counter connectedNodes = getNodeMetric(node, DefaultSessionMetric.CONNECTED_NODES);



Params:
  • profileName – the name of the execution profile, or null if the metric is not associated to any profile. Note that this is only included for future extensibility: at this time, the driver does not break up metrics per profile. Therefore you can always use getSessionMetric(SessionMetric) instead of this method.
Returns:the metric, or empty if it is disabled.
/**
   * Retrieves a session-level metric from the registry.
   *
   * <p>To determine the type of each metric, refer to the comments in the default {@code
   * reference.conf} (included in the driver's codebase and JAR file). Note that the method does not
   * check that this type is correct (there is no way to do this at runtime because some metrics are
   * generic); if you use the wrong type, you will get a {@code ClassCastException} in your code:
   *
   * <pre>{@code
   * // Correct:
   * Gauge<Integer> connectedNodes = getNodeMetric(node, DefaultSessionMetric.CONNECTED_NODES);
   *
   * // Wrong, will throw CCE:
   * Counter connectedNodes = getNodeMetric(node, DefaultSessionMetric.CONNECTED_NODES);
   * }</pre>
   *
   * @param profileName the name of the execution profile, or {@code null} if the metric is not
   *     associated to any profile. Note that this is only included for future extensibility: at
   *     this time, the driver does not break up metrics per profile. Therefore you can always use
   *     {@link #getSessionMetric(SessionMetric)} instead of this method.
   * @return the metric, or empty if it is disabled.
   */
  @SuppressWarnings("TypeParameterUnusedInFormals")
  @NonNull
  <T extends Metric> Optional<T> getSessionMetric(
      @NonNull SessionMetric metric, @Nullable String profileName);

  /**
   * Shortcut for {@link #getSessionMetric(SessionMetric, String) getSessionMetric(metric, null)}.
   */
  @SuppressWarnings("TypeParameterUnusedInFormals")
  @NonNull
  default <T extends Metric> Optional<T> getSessionMetric(@NonNull SessionMetric metric) {
    return getSessionMetric(metric, null);
  }

  
Retrieves a node-level metric for a given node from the registry.

To determine the type of each metric, refer to the comments in the default 
reference.conf (included in the driver's codebase and JAR file). Note that the method does not check that this type is correct (there is no way to do this at runtime because some metrics are generic); if you use the wrong type, you will get a ClassCastException in your code: 

// Correct:
Gauge<Integer> openConnections = getNodeMetric(node, DefaultNodeMetric.OPEN_CONNECTIONS);
// Wrong, will throw CCE:
Counter openConnections = getNodeMetric(node, DefaultNodeMetric.OPEN_CONNECTIONS);



Params:
  • profileName – the name of the execution profile, or null if the metric is not associated to any profile. Note that this is only included for future extensibility: at this time, the driver does not break up metrics per profile. Therefore you can always use getNodeMetric(Node, NodeMetric) instead of this method.
Returns:the metric, or empty if it is disabled.
/**
   * Retrieves a node-level metric for a given node from the registry.
   *
   * <p>To determine the type of each metric, refer to the comments in the default {@code
   * reference.conf} (included in the driver's codebase and JAR file). Note that the method does not
   * check that this type is correct (there is no way to do this at runtime because some metrics are
   * generic); if you use the wrong type, you will get a {@code ClassCastException} in your code:
   *
   * <pre>{@code
   * // Correct:
   * Gauge<Integer> openConnections = getNodeMetric(node, DefaultNodeMetric.OPEN_CONNECTIONS);
   *
   * // Wrong, will throw CCE:
   * Counter openConnections = getNodeMetric(node, DefaultNodeMetric.OPEN_CONNECTIONS);
   * }</pre>
   *
   * @param profileName the name of the execution profile, or {@code null} if the metric is not
   *     associated to any profile. Note that this is only included for future extensibility: at
   *     this time, the driver does not break up metrics per profile. Therefore you can always use
   *     {@link #getNodeMetric(Node, NodeMetric)} instead of this method.
   * @return the metric, or empty if it is disabled.
   */
  @SuppressWarnings("TypeParameterUnusedInFormals")
  @NonNull
  <T extends Metric> Optional<T> getNodeMetric(
      @NonNull Node node, @NonNull NodeMetric metric, @Nullable String profileName);

  /**
   * Shortcut for {@link #getNodeMetric(Node, NodeMetric, String) getNodeMetric(node, metric,
   * null)}.
   */
  @SuppressWarnings("TypeParameterUnusedInFormals")
  @NonNull
  default <T extends Metric> Optional<T> getNodeMetric(
      @NonNull Node node, @NonNull NodeMetric metric) {
    return getNodeMetric(node, metric, null);
  }
}